Thermostat construction



May 23, 1933. A DOBLE 3,911,066

THERMOSTAT CONSTRUCTION Filed May 5, 1950 IN VEN TOR.

A TTOR Patented May 23, @3335 PATE oric

ABNER DOIBLE, OF BERKELEY, CALIFGR'N'IA THERMOSTAT CONSTBUCTIBN Application filed Kay 5,

This invention relates to a thermostat for use with a fluid heater and particularly to a thermostat construction for employment with a fluid heater of the series tube or flash type.

The construction herein disclosed has been advantageously used with a series tube boiler utilized for the generation of steam and l shall therefore disclose it in this connection.

It has been the previous practice to control the temperature of steam in the boiler by means of an element inserted into the boiler tube so that it is in contact with steam in the boiler. This arrangement is satisfactory when steam is present and is in motion through the boiler. However, when the boiler throttle valve is closed and the steam is not in motion or, when there is no steam present, the rate of heat transfer to the element is very slow. Under these conditions 29 the temperature of the element lags behind the actual tem rature of the boiler tube. This allows the oiler tubing to heat up above the desired degree and, before sufficient heat has been absorbed by the element to makeup 95 for the lag, series damage to the boiler may occur due to overheating.

It is an object of the present invention to devise a thermostat construction which is responsive to temperature changes in the boiler all structure whether or not steam is flowing or is present.

A further object of the invention is to devise a relatively simple thermostat construction for use in determining and controlling the temperature of the steam.

The invention possesses other advantageous features and objects, some of which, with the foregoing, will be. set forth atlength in the following description where I shall outline in full that form of thermostat construction of my invention which I have selected for illustration in the drawing accompanying and forming part of the present specification. In said drawing 1 have shown one form oil thermostat construction embodying my invention, but it is to be understood that l do not limit myself to such form since the invention, as set forth in the claims, may be embodied in a plurality of forms.

in the drawing, Figure 1 is a diagrennnatic 1930. Serial No. 449,787.

view illustrating the thermostat construction of my invention and the manner in which it may be utilized to control the boiler.

Figure 2 is a section along the line 2-2 illustrating the structure of the thermostat. Figure 3 is a section through another form of construction of the thermostat.

My invention is characterized by the utilization of the fluid heater tube as a portion of the thermostat. Particularly, I make use of the tube to provide the motor or actuating element by forming a portion of the tubing so that expansions and contractions thereof are available 'torepresent the temperature changes. l have found that the temperature of the steam flowing through the tube follows, quite closely, the temperature of the tube wall. Therefore the en pensions and contractions of the tube are closely representative of the actual steam temperatures. By properly utilizing these variations which occur in accordance with changes in temperature, a thermostat element is available which represents the temperature of the flowing steam and, when the flow ceases, represents without any undue time lapse, the temperature of the tube wall.

In a successful form of the invention, as illustrated in Figure 1, a boiler 6 is. formed by a relatively? long tube which is enclosed in a casing 7. Water is introduced through inlet 8 and is controlled by awater inlet valve 9 normally biased to closed position by a spring ll. Steam generated in the boiler is discharged through an outlet 12 to be suitably employed.

Heat is supplied to the boiler by passing a current of air from a blower 1.6 through a venturi 17. At the throat of the venturi a carburetor 18 is positioned so that air forms an inflammable mixture with the fuel which is iited in the boiler. After the ignited air-fuel mixture has circulated through the boiler it is dischar through an exhaust hood 19 to the atmosphere. The blower 16 is driven by an electric motor. 21 which is included in a circuit with a battery 22 and a circuit breaker 23. This circuit breaher comprises a med contact 2% and a hinged contact arm 26 normally biased by a spring 27 to close the circuit.

eans, preferably res onsive to the tem perature of the boiler tu e, are provided for controlling the inlet valve 9 and the circuit breaker 23. A convenient form of. temperature responsive device is constructed by bending a portion of the boiler tube upon itself to form a loop 31 which surrounds a 10 thermostat tube 32. The thermostat tube,

usually made of the same material as the boiler tube, extends from the looped portion 31 to the outside of the casing 7 where it is secured to a' fixed support 33. The boiler tube and the thermostat tube are secured mechanically together. This is accomplished by filling the space between the'loop 31 and the tube 32 by welding 34 so that the loop 31 and tube 32 are formed into an integral g body 35.

In operation, the loop portion 31 and the thermostat tube 32 expand and contract as a single body in accordance with variations in temperature. This variation is made use 5 of, in accordance with my invention, by providing means having a different coeflicient of expansion from that of the integral body so that the variation is available to actuate suitable elements. In one form of my invention I employ a quartz rod 36. This rod is conveniently formed by inserting several quartz pencils into the tube 32 and holding them therein in abutment with the tube 32 by a rocker arm 37 biased by spring 38.

pon expansion or contraction of the integrally formed body 35, the quartz rod transmits such variations to the rocker arm 37.

This motion is utilized to control instrumentalities which effect the temperature of the boiler. Thus, upon an increase in the temperature of the integral body and the consequent expansion thereof, the quartz rod is moved leftwardly relative to the boiler casing by the sprlng biased rocker arm. Movement of the rocker arm causes it to engage the water inlet valve 9 to open it and allow water to enter the boiler. The introduction of the water usually suflices to lower the temperature. However, if it does not and further expansion of theintegral body takes lace, the rocker arm opens the inlet valve rther until it engages the contact arm 26 to break the circuit in which the motor 21 is included. This causes the supply of in flammable mixture to be shut ofl'.- The temperature is thereby prevented from exceeding a desired degree. The control is eflective whether steam is present or not While I have mentioned that I preferably employ a quartz rod it is to be understood that any suitable material having a different coeflicient of expansion from that of the integral body may be employed. Quartz has a relatively low coeflicient of expansion and is capable of withstanding high temperature.

Its employment simplifies the problem of utilizing the expansion and contraction of the tube to aflect the control element.

In the form of thermostat construction shown in Figure 3, a tube 41 of the boiler is joined by Welding at 42 to a thermostat tube 43 so that the two form an integral body. The quartz rod or rod of other material is placed in the tube 43 to effect the control element. This is a simpler construction and, where this is desired, it is particularly useful.

I claim:

1. In a boiler, a boiler shell, a boiler tube bent upon itself, a thermostat tube encompassed by and integrally joined to said boiler tube, means for joining said thermostat tubeto said shell, a substantially non-expansible rod within said thermostat tube, and a member actuated by said thermostat tube and .said rod.

2. In a boiler, a relatively long tube forming the boiler, a thermostat tube joined to the long tube mechanically to form an integral body, said body expanding and contracting upon changes in temperature, a substantially inexpansible element, and a member actuated by said element and said body.

3. In combination, a fluid conducting tube adapted to be heated, a second tube open to the atmosphere and welded to the first tube to form a thermally integral body, said body expanding and contracting upon variation in temperature, and a member Within said second tube expanding and contracting difi'erently from said body for transmitting the expansion and contractions of the body.

4. In combination, a fluid conducting tube adapted to be heated, a second tube open to the atmosphere and welded to the first tube to form a thermally integral body, said body expanding and contracting upon variation in temperature, and a member within said second tube for transmitting the expansion and contractions of the body.

5. In a boiler, a relatively long boiler tube, a thermostat tube joined to the long tube mechanically to form an integral body, said body expanding and contracting upon changes in temperature, and a rod positioned in the thermostat tube, said rod having a different coeflicient of expansion and transmitting contractions and expansions of the body.

6. Ina boiler, a tube into one end of which feed fluid is pumped and from the other end of which vapor issues, a member having a lower coeflicient of expansion than said tube, situated alongside said tube and arranged to transmit motions due to difl'erence in expansion of said tube and said member to control the fire and feed water of said boiler.

7. In a boiler, a tube through which heat absorbing fluid flows, said tube being in the form of two parallel portions between which a thermostat element having a different coeficient of expansion than said tube is located, and means to utilize relative motions between said tube and said element to control said boiler.

8. In a boiler, a tube through which heat absorbing fluid flows, said tube being in the form of two straight portions in parallel po sition and joined together at one end so that said fluid travels in one direction in one portion and in the reverse direction in the other portion, a thermostat element having a different coefiicient of expansion than said tube, located between said portions, and means actuated by difierences in expansion between said tube and said element to control said boiler. I

9. In a boiler, a relatively long boiler tube capable of expansion and contraction, means for supplying heat to the tube, means for extracting heat from said tube, and means for causing the expansion and contraction of said tube to control said supplying means and said extracting means.

10. In a boiler, a tube through which heat absorbing fluid flows, a member having a lower coefiicient of expansion than said tube arranged alongside said tube, and means to utilize relative motions between said tube and said element to control said boiler.

In testimony whereof, I have hereunto set my hand.

ABNER DOBLE. 

